The document proposes developing a miniature low-cost launch system called Microlaunchers to help advance space access technology. It would use a three-stage launch vehicle with each stage powered by staged combustion engines. The first stage would be recoverable via gliding to enable frequent low-cost launches. Future goals include developing small payloads to flyby asteroids and land on Near Earth Objects to gain navigational experience and advance capabilities. Developing the system incrementally and through partnerships is suggested.

1. CREATING A PATHWAY TO SPACE
Charles K Pooley
ckpooley@microlaunchers.com
ckpooley@sbcglobal.net
(702)438-5487
Blair J Gordon
blair@microlaunchers.com
willow7600@gmail.com
(614)434-6027

2. MICROLAUNCHERS
THE PREMISE
In view of recent events, it appears that entrepreneurial space is taking two main forms: suborbital
passenger service and low orbit satellites.
An example of the first is Scaled Composites and the newly formed Virgin Galactic. An example of the
second is SpaceX.
Both have in common a plan to make a profit in an expensive and uncertain environment. Much of the
stress and efforts of this type of venture will be centered around the investment/profit issues, with less
emphasis on the technology development, at the very time technology development is needed.
The Wright Brothers were not at first trying to set up a business. They were trying to build an airplane.
Microlaunchers is an attempt at a third approach to developing space access: to, with miniature size
and budget, develop a vertically integrated spacecraft launch/deployment system.
The system or portions of it then can be expanded with confidence after the initial system has proved
itself.

3. MICROLAUNCHERS
CURRENT DIRECTION
Space tourism is getting the most press because of the
recent X-Prize and plans to build a huge new industry.
It's not going to be that simple. If any of these do
actually start flying paying passengers, the business
and financial risks are so great that the effort will be
focused on making it succeed and not developing
access to space--to at least delivering people to a LEO
satellite.
"Tabletop spacecraft" refers to efforts to develop some
device, satellite, or even space a station module without
first developing the launch means. At the start of the
non-NASA space age, means to get there must come
first. An air show cannot precede the airplane.
The satellite launch service to deliver the current types
of satellites weighing hundreds to a few thousand
pounds will confront a problem: Those with such
satellites tend to have in their long involved construction
process the choice of available launcher already
factored in, together with the attendant costs.
Also, there are just too few of these to support a new
business centered around a new launcher. A good
example is the Orbital Sciences Pegasus air launched
system. In 15 years there have been a total of only 36.
Too few and infrequent to allow a launch cost
breakthrough.

4. MICROLAUNCHERS
SMALL & INEXPENSIVE
To develop a low cost basis from which an industry can evolve, a launch system must fly very
frequently and be very small.
I mean small: The Wright Brothers did not build a DC-3. They built something that barely carried two.
The launch system must be so simple to operate that some launchers might be kept on standby for
launch at a Near Earth Object--very small asteroids which pass by daily, some of which being
reachable for photo flyby. With a small in-house organization (Wright Brothers
being a good example) the components of the system
should be developed incrementally.
The testing and licensing of the stages should be done
incrementally, so each stage supports testing of the
next.

5. MICROLAUNCHERS
THE SYSTEM
The system needs to be complete, from launch to tracking and controlling the ascent, with initiating abort if
needed, to release of a detachable payload.
By perfecting a first generation of very small launcher/spacecraft combination, and using a high launch
rate the cost basis for all scaled up versions to follow would be minimized. Also, the skills to launch and
manage spacecraft would develop.
Later, with subsequent funding, a ten times increase of mass can enable a considerable increase in
payload mass. A second generation launcher with a gross liftoff mass ten times greater could allow a mass
of 50 pounds to escape velocity, allowing about 20 pounds to be soft landed on the moon or a Near Earth
Object.

6. MICROLAUNCHERS
LEO OR ESCAPE?
The Microlauncher system would not even get involved with Low Earth Orbit.

7. MICROLAUNCHERS
LAUNCH VEHICLE
The major component of the system is the launch vehicle. This is to use 3 stages, each using a type of
staged combustion engine derived from a single "prototype engine". The right funding might support
development of a staged combustion turbo pump engine, to be used for the first stage.

8. MICROLAUNCHERS
LAUNCH VEHICLE
The first stage is to deliver the upper two to an altitude having near vacuum conditions--about 60 to 70 Km
(200,000 to 233,000 feet), while having the vertical momentum to continue to about 100 Km. This "lofted"
trajectory permits a more horizontal attitude for the second stage, in a way similar to Shuttle launches. The
initially planned horizontal component is to be low for easy recovery and because the first stage, having
greater mass and lower specific impulse, will leave the task of accelerating to the upper stages. Here, 600
m/sec at 30 deg. latitude gives a possible eastward velocity of 1 Km/sec.
The second stage will operate in a vacuum, and have a higher specific impulse and lower empty mass
because the operating pressure can be lower and no aerodynamic provisions are needed. Carrying the third
stage, it is to increase the horizontal velocity by about 4 Km/sec. The structure will be mainly thin wall
aluminum tubing tanks and a low pressure engine. The tank pressure is to be about 10 atmospheres and the
engine pressure 5 atmospheres.
The third stage is to make use of very thin electroformed nickel structure and use a low tank and engine
pressure to allow a very low empty weight. The tank pressure is to be about 0.38 MPa (57 psia), the vapor
pressure of liquid oxygen at 105 deg K; and an engine pressure of about 0.15 MPa (1.5 atm). The low
pressures are to allow low mass and radiation cooling of part of the engine.
It is to accelerate and increase the horizontal velocity by about 6 Km/sec, so that the horizontal velocity will
exceed 11 Km/sec, the escape velocity from the altitude at which the third stage is out of propellants.
An optical guidance based on a camera looking at the sun and the earth horizon is to be carried on the
stage, and is to guide the second and third stages. Optical tracking from the launch site will enable
adjustment or termination of the flight.

9. MICROLAUNCHERS
LAUNCH VEHICLE
Recoverable First Stage
Shown here is the turbo pump engine version.
The structural layout of the pressurized
propellant version is more complicated because
it requires a larger number of smaller diameter
tank tubes.
In either case, there is to be two engines--one,
the "sustainer" of about 1000 pound thrust, and
the "booster of over 2000 pounds thrust. Both
operating together are to accelerate the
launcher to a high subsonic velocity, say, 250
m/sec, at which time the booster engine shuts
off and the sustainer continues. This is to allow
the small launcher to climb through the denser
part of the atmosphere quickly but without
aerodynamic loads becoming too high. This type
of ascent is more optimum for small vehicles
more subject to aerodynamic drag than the
usual larger launchers. It is not to reach
supersonic speeds until the altitude is over 5 to
10 Km.
The propellant tanks are the main structure, with
the engines and fins at the lower end, a "wing
box" at an adjustable point near the center of
gravity, and the upper stages within an
enclosure at the upper end. The wings are to
extend in a manner similar to those of a cruise
missile, after the stage has decelerated to a low
subsonic velocity.

10. MICROLAUNCHERS
LAUNCH VEHICLE
The Launch Trajectory
At launch there is a short high
acceleration period in which the velocity
reaches 250 m/sec in about 8 to 12
seconds at an altitude of about 2 Km
(6000 ft). The sustainer continues the
acceleration to the velocity of about
1200 m/sec (Mach 4), at which time the
engine is to throttle down to a low thrust
to maintain enough acceleration to keep
the propellants settled at the bottom of
each tank.
The stage is to orient itself to the pitch
for launch of the second stage at an
altitude of about 60 Km, while the
vertical velocity is still about 900 m/sec.
The second stage is to accelerate
nearly horizontally toward the east to
take advantage of the earth rotation of
about 400 m/sec if the latitude is 30
degrees.

11. MICROLAUNCHERS
LAUNCH VEHICLE
The Deceleration and Recovery
For recovery, airbrake panels are extended
and locked open at high altitude, and these
panels help the final velocity after reentering
denser air to become low enough for the
extension of wings to be done without too
much power required. The velocity might be
100 m/sec indicated speed (equivalent
speed at sea-level).
The wings are to extend and the brake
panels retract while the stage is still
descending vertically so there is no lift to
make the extension difficult. An on-board
accelerometer and gyroscope is then to
control a pullout maneuver at, say 3 G's, and
to finish the pullout with the stage gliding
horizontally.
A pitot tube on the nose is to then maintain a
steady glide speed of, say 40 m/sec (78
knots) by controlling the pitch. The stage is
then to glide in this way until it is picked up
and taken in tow by a small aircraft. The
towing force will be less than 50 pounds.

12. MICROLAUNCHERS
LAUNCH VEHICLE
The Propellant Management System Each propellant tank is to be a self
contained unit with a capacitive depth
sensor, shutoff valve and a motor driven
variable partially restricting valve.
A comparator circuit is to measure the
contents of each tank in turn at, say one
complete cycle each second, and cause an
incremental increase in opening of the
valve of the tank least depleted. In each
cycle the tank most depleted will have its
valve closed by a small increment. This is
to cause all the tanks to drain together,
with little or no residual of contents. This
will work with any number of tanks and any
number of propellants (a first stage version
might use water as coolant).

13. MICROLAUNCHERS
LAUNCH VEHICLE
Staged combustion engines
The engines are to use a 'pre-burner' to
change the LOX to a high pressure gas which
is to enter the engine at perhaps 100 m/sec.
This will facilitate the atomization of the fuel
and permit a wide range of throttling, because,
in lowering the thrust only the oxygen gas
pressure changes, not its volume. The range of
thrust may be more than ten to one.
The preburner is to be able to operate by itself,
using servos to control the temperature and
pressure of the oxygen. The oxygen is to pass
through a nozzle in order to isolate the
preburner from the combustion chamber
downstream. An oxygen to fuel ratio of 100 to
1 will produce a gas temperature of about 60C.

14. MICROLAUNCHERS
LAUNCH VEHICLE
Staged combustion engines (cont.)
The preburner will then be coupled to the remainder of a test engine in order to test the fuel atomization and
a property called characteristic velocity--an indicator of the engine performance.
The test engine will be water cooled with measurement of the heat conducted from the chamber being
measured. This is to confirm the choice of regenerative cooling method.
The numbers given here are preliminary
estimates that the prototype engine is to
confirm. The engines for all three stages are
to then be designed as a scaling up or down
of size and pressure. If funds are found to first
develop a turbo pumped engine, that will be
used for the first stage.

15. MICROLAUNCHERS
LAUNCH VEHICLE
Staged combustion engines (cont.)
The third stage is to be constructed almost entirely of electroformed nickel. With this method there is no
"minimum gauge problem"--the problem of finding materials that are thin enough for small low pressure
tanks.
The LOX and propane fuel tanks are to use three identical nearly spherical shells coupled in a way to be
published later.
The propellants and a small capsule of liquid
nitrogen will be kept at 105 degrees K, at which
the pressures of the three liquids will determine
the feed rate and engine pressure.
The engine is to operate with a low chamber
pressure--perhaps slightly higher than one
atmosphere, so that the lower heat flux will allow
major parts of it to be radiation cooled at a
reasonable temperature.
This low chamber pressure will also allow more
extensive testing, designing of the injector and
combustion chamber in a testing environment that
is simpler than the usual test stand.

16. MICROLAUNCHERS
AFTERNOON LAUNCH
The path likely for a successful launch slightly over the escape velocity and using an eastward launch in the
late afternoon will become a slightly elliptical solar orbit, with most of it being beyond Earth's orbit. This way,
it will tend to be in line-of-sight at night for the first 6 months or so.
After confirming a velocity in excess of
escape minutes to an hour or so after
launch, the main next stage in developing
the Microlauncher system will be the means
to keep a detached payload oriented and in
communication with a place on Earth. The
plans for developing this will be published
later.

17. MICROLAUNCHERS
FLIGHTS / MISSIONS
At first, the launches will be centered around the launcher performance, and there would not be a
detachable payload. The launchers will support spacecraft development, diode laser link tests, and perhaps
to pursue some revenue possibilities such as sending to solar orbit samples of cremated remains. With an
in-house launcher, this becomes a possibility.

18. MICROLAUNCHERS
FLIGHTS / MISSIONS
Later, there would be tests of a spacecraft structure which can maintain 3 axis orientation with
solar radiation pressure and no use of consumables, and a point able laser diode data link. The
data link design details will be published later.
Then, a small cold gas thruster system using room temperature ammonia will be designed to
give a velocity deviation capability of 100 m/sec.
A complete spacecraft might have built in the electronics of an off-the-shelf digital camera.
Stripped of the packaging, these weigh very little and can offer megapixel quality images rivaling
those from NASA not many years ago.
The issue of radiation hardening can be explored by observing the condition of the electronics
over months. Many NEO's can be reached in a relatively short time, so commercially available
electronics may last long enough to be useful.
Another important product of many cheap launches will be the development by a substantial
number of people the navigational skills which are vital to opening access to the solar system.
This is what happened with computers. Millions have them and have developed the skills to use
them. A social revolution.

19. MICROLAUNCHERS
FLIGHTS / MISSIONS
Some NEO's (which could someday be called Microlauncher targets) pass Earth at a velocity low enough so
that rendezvous and controlled landing may be possible. The guidance for such a lander can make use of
the chips used in an optical mouse. Because of the way they operate, the guidance will tend to allow the
approach velocity, deceleration and distance to converge on zero together so the craft would not bounce off.
The escape velocity of many of NEO's is less than 1 foot/sec.
The guidance might use a small diode laser as
a LIDAR, and one mouse chip to control the
transverse movement while the LIDAR controls
the descent. Or it could be wholly passive,
using 3 or 4 mouse chips which together
measure the movement in 3 axes.

20. MICROLAUNCHERS
DEVELOPMENT
The project and funding of it will be done
in a piecemeal fasion, possibly combining
with partners interested in a development
of one or more of these subsystems.
SBIR or DARPA funding might likewise be
sought for a subsystem as a separate
project. In time, it is hoped that this will
eventually add up to the Microlauncher
System.

21. MICROLAUNCHERS
ENGINE
The first stage of the small Microlauncher will probably use a pressurized propellant system, but for a scaled
up launcher, a turbo pump type engine would avoid the need of large high pressure tanks and to take
advantage of the higher performance and lighter structural weight possible.
If a partner were to be found who was interested, this engine type might be developed earlier and used in
the small Microlauncher.

22. MICROLAUNCHERS
ENGINE
The preburner developed for the upper stage engines would be scaled up in size and pressure to drive a
turbine with oxygen gas at a moderate temperature, say, 500 to 600 K (230 to 330 C) so the materials for
the turbine and associated parts can be of copper, bronze, or monel. The Russian RD-170 uses an oxygen
temperature of 772 K in order to get the power to support a very high chamber pressure. For a lower
pressure of, say, 3.3 MPa (500 psi), calculations show that the lower temperature is sufficient.
As with the non-turbopump type, the high velocity oxygen will allow effective atomization of the fuel, or
possibly there might be a fuel preburner which uses some of the LOX from the pump to heat the fuel enough
so it enters as a gas or supercritical fluid. Having no surface tension the fuel will not form drops and no
atomization will be required.
The design process is still underway, but it appears that this engine type can be throttle able over a wide
range and be lighter and more efficient than the pressurized type.
Incidentally, I am using SI measurements for the actual design calculations because pounds, slugs, pound,
square feet etc is just too confusing. Also, English units caused loss of a Mars orbiter once.

23. MICROLAUNCHERS
ENGINE
The preburner developed for the upper stage engines would be scaled up in size and pressure to drive a
turbine with oxygen gas at a moderate temperature, say, 500 to 600 K (230 to 330 C) so the materials for
the turbine and associated parts can be of copper, bronze, or monel. The Russian RD-170 uses an oxygen
temperature of 772 K in order to get the power to support a very high chamber pressure. For a lower
pressure of, say, 3.3 MPa (500 psi), calculations show that the lower temperature is sufficient.
As with the non-turbopump type, the high velocity oxygen will allow effective atomization of the fuel, or
possibly there might be a fuel preburner which uses some of the LOX from the pump to heat the fuel enough
so it enters as a gas or supercritical fluid. Having no surface tension the fuel will not form drops and no
atomization will be required.
The design process is still underway, but it appears that this engine type can be throttle able over a wide
range and be lighter and more efficient than the pressurized type.
Incidentally, I am using SI measurements for the actual design calculations because pounds, slugs, pound,
square feet etc is just too confusing. Also, English units caused loss of a Mars orbiter once.